Drop Tower Project 2018

James Cudworth, Emily Paul, Andrew Pocklington

Drop Tower Background

• A Drop Tower is a large structure, usually evacuated, used to allow objects in free fall to simulate zero-gravity environments
• Examples:

2.2 second Drop Tower at the Glenn Research facility operated by NASA

4.74 second ZARM Drop Tower at the University of Bremen in Bremen, Germany

Yerkes Vacuum Tube

• The Yerkes Vacuum Tube was constructed in the early 1990s as a light path for the experiments of Professor Walter Wild of the University of Chicago
• It is approximately 34 ft long, made of stainless steel, and begins in the 41’’ dome terminating in the 41’’ basement

Initial Vacuum Tube Status

• The tower itself was not perfectly vertical; originally being a light path,
• The angle margin of error was about half a degree
• The bottom of the pipe was offset by about half its diameter
• Two PVC pipes ran next to the tube, prohibiting its movement
• The pump was entirely disconnected and housed in another room
• The plates being used to cap the ends were still glass lenses
• A feasibility study conducted two years prior had found that conversion to a drop tower would be possible

Vacuum Pump

• When the pump is attached to the drop tower, it can maintain a vacuum of about .05 Torr, equal to NASA’s Glenn Drop Tower standard

Tube Alignment

• Corrected to within about .07 degrees (about .5” offset)
• Can successfully drop a 4.5” diameter object through 6” diameter tube
• The tube was aligned with a plumb line, level, and collimating laser
• Plots were taken correlating points at the bottom of the tube to points at the top

Drop Experiments Performed

• To test the maximum carriage size allowed, dropped 3D printed test circles and listened for impacts into the wall of the tube.

Retrieval Mechanism

• Eliminates need to access top of drop tower before each experiment
• 12V, 9 RPM motor used with a gear ratio of 32:13
• Can lift experiments through tube in about 2 minutes
• Button built into assembly stops motor as soon as electromagnet is correctly placed

Guidance and Release Mechanism

• The red bracket can rotate a full 360°, while its slots allow the silver circle to slide from the center to the outside edge of the bracket
• A white cone attached to the eye bolt fits exactly into the conical opening in the guide
• The purple plate triggers the button which will stop the motor

Braking Mechanism

• 2 ft piece of aluminum pipe filled with EPS pellets
• Gently decelerates an experiment from about 15 m/s (34 mph) to 0
• Objects experience around 16G while decelerating
• The two foot extension is currently mounted on a scissor jack for ease of removal

Future Modifications

• Complete carriage construction, perform drop clearance and deceleration tests
• Assemble control panel and related wiring
• Refine tube alignment
• Hermetic door on dewar at top
• Hermetic chamber with door at bottom of tube
• Large gate valve to maintain vacuum in upper portion of tube

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